Solid ink or phase change ink printers encompass various imaging devices, such as printers and multi-function platforms. Solid ink printers offer many advantages over other types of image generating devices, such as laser and aqueous inkjet approaches. These advantages include higher document throughput, sharp colors, and less packaging waste for the ink consumed by the printer.
A typical solid ink imaging device includes an ink loader, which receives solid ink units, such as ink sticks or pellets. These ink units remain solid at room temperatures so a user can conveniently store solid ink in proximity to a device and handle the solid ink during the loading phase without mess or staining. Coupled to the ink loader is a feed channel through which multiple units of the solid ink may be transported for delivery to a melting assembly. Thus, the ink is loaded by a user in solid form into the ink loader and then the solid ink is moved into the feed channel for delivery to the melting assembly. In most color solid ink imaging devices, a plurality of ink loaders are provided, one for each color of ink used in the device. Coupled to each ink loader is a feed channel for delivering the solid ink from an ink loader for a particular color to a melting assembly for that color. These multiple ink loaders, feed channels, and melting assemblies are typically provided in parallel in the imaging device.
Movement of the solid ink from the ink loader to the feed channel has been previously performed in a variety of ways. In some solid ink printers, the loader includes an insertion port at an upper end of a feed channel. An ink stick is placed in the port so that at least a portion of the ink stick engages a mechanized drive, such as an endless belt mounted around driven pulleys. As the pulleys are driven by a motive force, such as an electrical motor with a rotational output shaft, the belt transports the ink stick along the feed channel. The feed channel may terminate in a nearly vertical section. The end of the looped belt furthest from the insertion port is proximate the vertical section. As the ink stick leaves the driven endless belt, it transitions to a vertical orientation so gravity pulls the ink stick to the bottom of the feed channel against a melting assembly. The melting assembly causes the solid ink to change phase and be collected in a reservoir for use in the printer.
Solid ink or phase change printers differ from ink cartridge or toner printers because the colorant supply is manually manipulated by the user and the supply need not be exhausted before the supply is renewed. Specifically, ink cartridges and toner cartridges require exhaustion because they are storage containers that cannot be refilled by the user. Instead, the cartridges are typically returned to the manufacturing source to be refilled. Solid ink, on the other hand, may be stored on the premises and installed a unit at a time into the imaging device. Because the entire solid ink unit is consumed in the printing process, no housing or other component survives for return to the manufacturer.
The requirement that the solid ink units remain solid until they impinge upon the melting assembly does present some challenges not present in the ink cartridge and toner cartridge printers. While the ink loader is essentially within the ambient room temperature environment, the melting assembly is elevated above this temperature to one that causes the solid ink unit to change phase. Typically, the melting assembly is located within the interior of the printer, while the ink loader is located at the exterior of the printer so the user can access the loader. After the solid ink is inserted, it then needs to be transported from the loader to the melting assembly.
In the loading systems that include a mechanized drive and a gravity fed section, the feed channel can appear full to a user when the feed channel has gaps between the ink sticks. This situation is depicted in FIG. 1. As shown in the figure, a curved feed channel 14 includes an endless belt 18 mounted around pulleys 20 at least some of which are driven by a motor and gear train 22 or the like. An ink stick 26 placed in the port 24 engages the belt 18 and is carried along the feed channel 14 in response to the pulleys 20 being driven. After transitioning through the curve 28, the ink stick begins a fall towards a melting assembly 30. As shown in FIG. 1, a stack of ink sticks may develop in the gravity fed portion of the feed channel 14. The weight of these sticks help urge the bottommost stick against the melting assembly for more efficient melting.
In order to sense the presence of ink sticks in the vertical section of the feed channel 14, one or more mechanical flags may be provided. As shown in FIG. 1, a low ink flag 36 is positioned near the end of the transition section and an out of ink flag 40 is positioned near the melting assembly. The mechanical flag may be a finger that is biased to move into the ink stick path. An ink stick moving through the feed channel 14, however, urges the flag against the biasing action to displace the flag from its path as it passes a flag. The presence of the flag may be electrically sensed to generate a signal that indicates whether an ink stick is acting on a flag or not. For example, if the low ink flag indicates no ink stick is acting on it to move it out of the ink stick path, then a signal is generated that indicates only a number of ink sticks corresponding to the length of feed channel below the low flag to the melting assembly may be present in the feed channel. Similarly, if no ink stick is acting on the out flag, then an insufficient amount of ink stick is in the vertical portion of the feed channel to provide a reliable supply of solid ink to the melting assembly for use in the printer. In response to the signal generated from the low flag or out flag indicating no ink stick is opposite the flag, a controller in the printer may activate the motive force to the pulleys 20 to transport ink sticks to the vertical section of the feed channel to replenish the stack of ink sticks against the melting assembly.
As shown in FIG. 1, waiting for a signal to be generated in response to the flags may result in a gap G between the sticks in the vertical section of the feed channel and the sticks near the insertion port. In response to the ink low or ink out signals, the motive force drives the belt until one or both of the signals change state to indicate a solid ink stick is opposite the flag. The delay between the flag changing state and the motive force being stopped may result in the belt rotating against one or more ink sticks that cannot move because the vertical section has been filled. This rotation against a stationary ink stick may produce some debris in the feed channel. This debris is solid ink that is lost to the ink supply process. Also, as ink sticks are driven to the transition section of the feed channel, the fall through the vertical space caused by the gap may also cause collisions between ink sticks that also result in solid ink being lost to the ink supply process. Consequently, a solid ink stick transportation system that provides a continuous supply of solid ink to the melting assembly and leaves the gap at the insertion port where the user can view it is desirable.